1. Field of the Invention
The present invention generally relates to a method for reinforcing, consolidating and stabilizing a predetermined area in the ground to improve sandy soil and soft ground in building site, underground construction scene, sea side and mountain zone. More particularly, the present invention relates to an improvement in a method of all-around type reinforcing and consolidating work which is adapted for any angle works such as vertical, slant and horizontal works. Further, the present invention relates to an apparatus for performing the above described method.
2. Description of the Prior Art
Conventionally, various methods for reinforcing and consolidating the soil or soft ground have been developed and used to make underpinnings and hard foundations in a building site and other constructing sites in mountains and sea sides. Especially in urban area, it has been quickly required to develop new systems for the construction works in an extremely deep underground. For instance, an underground train, an underground high way, an underground commercial street, an underground parking site, etc. have been recently proposed as a practical plan to make efficient use of highly closed built area in large cities. However, most large cities are constructed on the alluvial soft ground which requires an effective reinforcing, consolidating and stabilizing system capable of satisfying complicated construction works in the extremely deep underground.
On the other hand, a commonly used method of various ground-consolidating works includes at least one of injecting systems using pressurized water, air, and hardening material. As an example, CCP-Method; trade name by Wataru Nakanishi, 1970, has been broadly known. Further improved systems of CCP-Method have been proposed and employed in various scenes. Such improved systems are modifications of the above CCP-Method varied in the pressure and rate of injection, and combination with pressurized air. Most of these improved systems are intended to enlarge the diameter of consolidated area in ground.
However, most of such conventional methods are designed for mainly vertical work with increment of injection pressure, injection rate and jetted air. In the case of works in extremely deep underground or horizontal direction, the injected water and air, and resulted slurry make the pressure in the ground become high because the injected water and air, and the slurry can not be smoothly discharged from the working space. Therefore such conventional methods can not be directly used for all-around conditions Such as the works in extremely deep underground or horizontal direction.
In detail, according to an experimental example in which one conventional method was used for a horizontal work and a slant work, discharging phenomenon of the resulted slurry from the working area through opening space around the working device was stopped at about four minutes after starting. Then the ground surface of working position was slightly rised, and as a position was slightly raised, and as a few minutes passed, the discharged slime was effused out of the ground surface apart from the working position. This resulted in undersirable irregular consolidation owing to the following reason.
The slurry to be discharged from the working area can not be smoothly discharged while the pressurized water, hardening material, air and so on are continuously injected into the working area. Further, since the pressurized air is mixed with the slurry, the air in the working area can not be discharged in the horizontal direction and a tendency to move upwardly occurs. Thus the pressurized air is remained in the working space. The lingering air causes the consolidation to be irregular and the slime and slurry to effuse.
On the other hand, the ground reinforcing and consolidating method includes an excavating step prior to the injection step of the pressurized hardening material and air, and most of the conventional excavating devices used in the excavating step are not provided with any protectors or guards. Accordingly the body and bit of the excavating device are often damaged in the excavated cavity formed in the deep underground. Further the excavating device and the injecting device must be combined in a single rod-shape body so that the injecting device can not be provided with an additional mechanism such as a pressure sensor.
In order to overcome these defects of the conventional methods, the applicant of this invention has already proposed, as Japanese Patent Application No.3-288248/1991, an improved method of all-around type reinforcing and consolidating work which is adapted for any angle works such as vertical, slant and horizontal works especially effective in the extremely deep underground. This all-around type working method is called MJS (Metro Jet System); the trade name registered by the applicant. The present invention belongs to this MJS type working method. Of course, this MJS type working mehod can be performed an improved all-around type reinforcing and consolidating apparatus.